Hydrogen energy has a high combustion value, zero pollution, rich elements, and other advantages, thus becoming the most potential secondary energy to replace the traditional fossil energy. The large-scale development and utilization of hydrogen energy is expected to solve the current double problems of environmental degradation and energy shortage, but the three major issues of hydrogen production, storage and application have to be solved first. The method of releasing hydrogen from a hydrogen storage alloy, in addition to the reverse reaction of a hydrogenation reaction, also includes producing hydrogen by a hydrolysis reaction, which, compared with the former, has poor reversibility, but can displace an H atom from H2O in the hydrolysis reaction, making the amount of produced hydrogen greatly increased. And hydrolysis production of hydrogen has the characteristics of producing hydrogen on site, using pure water as raw materials, needing no heat and pressure regulation, convenient and fast application, and safe operation. The NaBH4-based instant hydrogen supply system launched by American Millennium Cell Company in 2001 is successfully applied to the Chrysler sodium fuel cell concept car, confirming the practicality of instant hydrolysis supply of hydrogen. Due to the many advantages of hydrolysis production of hydrogen, hydrolysis devices for hydrogen production will inevitably occupy a place in the large-scale use of hydrogen energy.
The goal set by U.S. Department of Energy (DOE) for the vehicle hydrogen storage system is that the hydrogen storage mass density is not less than 6.5% and the hydrogen storage volumetric density not less than 62 kg H2/m3, for which the relatively light-mass elements should be used; taking into account the safety and availability of raw materials, CaMg2 alloy has great potential. It has a theoretical hydrogen content of 6.3 wt %, and have wide raw material sources and low prices; however, its hydrogen absorption temperature is too high, and its hydrogenation reaction produces of CaH2 and MgH2 are low reversibility. It was reported that CaH2 and MgH2 were subjected to hydrolysis reaction after ball milling, in which CaH2 could effectively improve the hydrolysis rate and degree of MgH2, with 80% of the theoretical hydrogen production reached after 30 min. If CaMg2 is used as the raw material, producing dispersed CaH2 and MgH2 in situ after hydrogenation will help to improve the kinetic properties of the hydrolysis.
But high temperature and high pressure are needed for CaMg2 to be hydrogenated, and having high hydrogenation reaction activation energy. How to reduce its activation energy will become very important in the industrial production. It is the technical problem currently to be solved to cost less energy to obtain the hydride thereof and then produce hydrogen by hydrolysis.